1. Field of the Invention
The invention relates to a detection apparatus for a vehicle, such as an automobile, and more particularly to a tire force detection apparatus that detects a force exerted on a tire of a tire/wheel assembly.
2. Description of the Related Art
Various tire force detection apparatuses that detect the force exerted on a tire of a tire/wheel assembly in a vehicle, such as an automobile, have already been proposed. For example, Japanese Patent Application Publication No. 2005-241470 (JP-A-2005-241470) describes a tire force detection apparatus, in which axle-side connecting members and wheel-side connecting members are alternately disposed at four positions that are arranged in the circumferential direction around the rotation center of the tire/wheel assembly, an elastic member and load sensors for detecting the load that is applied to the elastic member are provided between the axle-side connecting members and the wheel-side connecting members, and the force exerted on the tire is calculated based on the result of detection by the load sensors.
WO2008/133353 proposed by the present applicant describes a tire force detection apparatus that has a stress detecting means that detects the stress that is applied to a connecting means for connecting a disc portion of a wheel of a tire/wheel assembly and a wheel support portion of a wheel support member, and a calculation means that calculates the tire force based on the stress detected.
In the tire force detection apparatus described in JP-A-2005-241470, stress is transmitted between the wheel-side connecting members and the axle-side connecting members through the elastic member. In the tire force detection apparatus described in WO2008/133353, stress is transmitted between the disc portion of the wheel and the wheel support portion through the connecting means and the stress applied to the elastic member and the connecting means are detected.
Thus, when the stiffness of the elastic member and the connecting means is set low so as to increase the S/N ratio in detecting the force exerted on the tire, the mounting stiffness of the tire/wheel assembly is reduced. On the other hand, when the stiffness of the elastic member and the connecting means is set high in order to secure a favorable mounting stiffness of the tire/wheel assembly, the S/N ratio in detecting the force exerted on the tire is reduced and it becomes difficult to detect the force exerted on the tire with high accuracy.